Whether you're a bird person or not, this is stunning!!!
Not to detract from the sheer magic of it, but in practical terms, how M A NY trips would a bird have to make with that tiny little quantity of mud/clay it could carry? (and how far from the nest is the source?)
If you take the construction of a circular bowl in your stride as instinctive how the heck does the bird come up with the windbreak/entrance design that shields the eggs/chicks from the elements and at what point in fashioning the bowl do they start to construct it?